Isolating functional molecules or substances in inert materials has many useful benefits and applications where chemical contact between the active ingredient and the immediate environment should be minimized. For example, make-up compositions, such as make-up colors are currently using a very limited number of approved natural pigments and even fewer artificial organic colors. Many dyes and pigments with desired color shades of natural or synthetic origin are not approved for skin contact because their safety for direct skin contact has not been demonstrated. Isolating the colorants in a transparent and inert isolating material provides a way to prevent the direct contact between the color molecules and the skin, while retaining (or even enhancing) the color intensity. Another very important application is in sunscreen compositions. The active ingredients in sunscreens have been reported to cause contact dermatitis and may cause photo contact dermatitis. Moreover, the light-excited species of these reagents may undergo photodecomposition reactions resulting in the production of free radicals and reactive oxygen species, which may bear deleterious effects on live tissues. Thus, encapsulating sunscreen active ingredients by enveloping them within a transparent silica shell offers a sophisticated way to benefit from the light-absorbing capability of sunscreens, while substantially isolating them and/or their possible photodecomposition products from the live tissues. Another example, from a totally different field, is the encapsulating of food colors either for prolonging the shelf life of food products containing unstable natural colors such as lycopene and carotene or for isolating artificial food colors that have undesirable side effects. Encapsulating food colors of the second type in inert transparent microcapsules provides a way to prevent the digestion of these colorants while maintaining their desired color effect.
U.S. Pat. Nos. 6,303,149, 6,238,650, 6,468,509, 6,436,375 and International publication Nos. WO 01/80823, WO 03/034979 and WO 03/039510 (the disclosures of these patents and publications are incorporated herein by reference in their entirety), disclose sol-gel microcapsules and methods for their preparation. In these patents and publications the loading of the active ingredients (termed also “functional molecules”) which constitutes the core of the microcapsules is up to 95% (w/w).
U.S. Pat. No. 6,365,642 discloses a process for obtaining open-celled foams by polymerizing a high internal phase (water-in-oil) emulsion, which has small amount of a continuous oil phase and a relatively greater amount of discontinuous phase. The water-in-oil emulsion taught cannot be used to form sol-gel microcapsules since the oil constitutes the external phase.
EP 0934 773 relates to microcapsules, wherein the capsule wall is composed of organopolysiloxane, and to a method for producing such micro capsules.
There is a widely recognized need and it will be highly advantageous to have microcapsules comprising a high concentration (above 95% w/w) of the core material (which includes the active ingredient) and yet which is capable of minimizing the contact between the active ingredient and the environment. Such high concentration of the core material is required, for example, in order to obtain high Sun Protection Factor (SPF) values, or in many other applications where high loading of an encapsulated active ingredient in the composition is required.
Additionally it will be highly advantageous to have an efficient encapsulation method which is simplified in production lower in cost (i.e involving less monomer and less waste disposal) and which is capable of having high concentrations (above 95% w/w) of the core material (active ingredient) and yet preventing the leaching of the active ingredient from the microcapsules. Such a method will facilitate the encapsulation of a wide variety of molecules or substances, where the application may demand high loading of the encapsulated molecules or substances.
Moreover, it will be highly advantageous to have an oil-in-water emulsion having a high concentration (above 50%) of the internal oily phase and to have emulsions which is simplified in production.